Polyester nonwoven fabric and method for manufacturing the same

ABSTRACT

Disclosed are a polyester nonwoven fabric which can be used as an useful primary backing substrate for a carpet since it exhibits good physical properties even after tufting process, and a method for manufacturing the same. The polyester nonwoven fabric of the present invention comprises an one-component filament and a sheath-core type filament both of which have a fineness of 4 to 10 denier. The one-component filament comprises a first polyester polymer having a melting point of 250° C. or higher, the sheath-core type filament comprises the first polyester polymer of 70 to 95 wt % as a core component and a second polyester polymer of 5 to 30 wt % as a sheath component, and a melting point of the second polyester polymer is lower than the melting point of the first polyester polymer by 20° C. or more.

TECHNICAL FIELD

The present invention relates to a polymer nonwoven fabric and a method for manufacturing the same, and more particularly, to a polyester nonwoven fabric which can be used as an useful primary backing substrate for a carpet since it exhibits good physical properties even after tufting process, and a method for manufacturing the same.

BACKGROUND ART

Carpets generally comprise a primary backing substrate and a face yarn. The face yarn penetrates the primary backing substrate to form tufts projecting from one side, providing a pile surface, and stitches on an opposite side. Carpets typically are made by tufting a face yarn through a primary backing substrate with reciprocating needles that carry the face yarn back and forth through the primary backing substrate to form tufts and stitches.

A polyester nonwoven fabric comprising polyester filaments is widely used as a primary backing substrate. During the tufting process, however, some filaments constituting the polyester nonwoven fabric are damaged by the reciprocating needle, which causes the deterioration of the physical properties such as strength, elongation, and tearing strength of the nonwoven fabric.

Any of the methods proposed so far to overcome such drawbacks is not satisfactory from the technical viewpoint and from the commercial viewpoint as well.

For example, Korean Patent Application Laid-Open No. 1998-0061102 discloses a method for manufacturing a spunbond nonwoven fabric for a primary backing substrate for a carpet, the method comprising forming a web with two kinds of polyester polymers, needle-punching the web, and then passing the needle-punched web through a calendar roll. However, the whole processes of this method is so complicated. Furthermore, some filaments are damaged when the web is needle-punched, which makes the problem of the damages of the filaments after the tufting process more serious. As a result, a nonwoven fabric produced by using such method as described above still has a problem of serious deterioration of the physical properties thereof after a tufting process, and thus it can hardly be used as a primary backing substrate for a carpet.

As an another example, Korean Patent Application Laid-Open No. 2001-0053138 describes a method for manufacturing a primary backing substrate for a carpet, the method comprising conjugate spinning polyester and polyactic acid to form a shaped yarn. However, the shaped yarn produced as such is likely to have lots of spinning defects caused by the bad spinnability. Furthermore, the use of the expensive polyactic acid inevitably increases the whole cost for manufacturing the nonwoven fabric.

Accordingly, it has been continuously required to produce a nonwoven fabric through simple processes and at lower cost, which exhibits good physical properties even after a tufting process and thus can preferably be used as a primary backing substrate for a carpet.

DISCLOSURE Technical Problem

Therefore, the present invention is directed to a polyester nonwoven fabric and a method for manufacturing the same capable of preventing problems due to such limitations and drawbacks of the related art as explained above.

An aspect of the present invention is to provide a polyester nonwoven fabric which can be used as an useful primary backing substrate for a carpet since it exhibits good physical properties even after tufting process.

Another aspect of the present invention is to provide a method for manufacturing a polyester nonwoven fabric which can be used as an useful primary backing substrate for a carpet since it exhibits good physical properties even after tufting process, through simple processes and at lower cost.

Additional advantages, objects, and features of the present invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof.

Technical Solution

According to one aspect of the invention, there is provided a polyester nonwoven fabric comprising: an one-component filament having a fineness of 4 to 10 denier; and a sheath-core type filament having a fineness of 4 to 10 denier, wherein the one-component filament comprises a first polyester polymer having a melting point of 250° C. or higher, wherein the sheath-core type filament comprises the first polyester polymer of 70 to 95 wt % as a core component and a second polyester polymer of 5 to 30 wt % as a sheath component, and wherein a melting point of the second polyester polymer is lower than the melting point of the first polyester polymer by 20° C. or more.

According to another aspect of the invention, there is provided a method for manufacturing a polyester nonwoven fabric, the method comprising: spinning a first polyester polymer to form an one-component filament; conjugate spinning the first polyester polymer and a second polyester polymer to form a sheath-core type filament, the first polyester polymer being a core component and the second polyester polymer being a sheath component; forming a web with the one-component filament and the sheath-core type filament; and heating the web so that the one-component filament and the sheath-core type filament can be bonded to each other.

The general description provided above and the detailed description provided below are only for illustration of the present invention and should be construed as providing a more detailed description of the inventions defined in claims.

Advantageous Effects

A polyester nonwoven fabric of the present invention exhibits excellent physical properties such as tensile strength, elongation, tearing strength and so on even after a tufting process is performed thereon. Thus, the polyester nonwoven fabric of the present invention can be used as an useful primary backing substrate for a carpet.

Additionally, according to the present invention, the filaments of a web can be bonded to each other by a simple process of heating the web. In other word, according to the present invention, it is not required to perform a needle punching process for web bonding. Thus, the polyester nonwoven fabric of the present invention can be manufactured through simple process at lower cost.

Other effects of the present invention will be described in detail below together with the technical features associated therewith.

MODE FOR INVENTION

Hereinafter, the embodiments of present invention will be described and explained in detail only for illustrative purposes. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. Accordingly, the present invention includes all alternations and modifications that fall within the scope of inventions described in claims and equivalents thereto.

A nonwoven fabric of the present invention comprises an one-component filament having a fineness of 4 to 10 denier and a sheath-core type filament having a fineness of 4 to 10 denier.

The one-component filament comprises a first polyester polymer having a melting point of 250° C. or higher. It is formed by spinning a single dope including the first polyester polymer.

The sheath-core type filament comprises the first polyester polymer as a core component and a second polyester polymer as a sheath component. That is, the sheath-core type filament comprises, as a core component, the same polyester polymer as that of the one-component filament. The second polyester polymer, a sheath component of the sheath-core type filament, has a melting point lower than the melting point of the first polyester polymer by 20° C. or more. That is, the core component of the sheath-core type filament has a melting point higher than that of the sheath component.

Since the sheath-core type filament of the nonwoven fabric of the present invention comprises the second polyester polymer having a relatively low melting point as a sheath component around the surface thereof, it can be easily bonded to the one-component filament when heated. Therefore, according to the present invention, the filaments can be easily bonded to each other, without a needle punching process performed, enabling the nonwoven fabric to be made through simple processes without any damages of the filaments which would be caused should the needle punching process be performed.

Furthermore, since the polyester nonwoven fabric of the present invention further comprises the one-component filament in addition to the sheath-core filament, the movement of the filaments can be guaranteed in a certain degree when a tufting process to make a carpet is performed, and thus the damage of the filaments, if any, that might be caused by the reciprocating needle during the tufting process can be minimized. As a result, if the nonwoven fabric of the present invention is used to make a carpet, as compared to a nonwoven fabric having only sheath-core type filaments, the damage of the filaments that might be caused by the reciprocating needle during the tufting process can be minimized, and the excellent physical properties such as tensile strength, tear strength and so on of the nonwoven fabric can be maintained after the tufting process.

The one-component filament and the sheath-core type filament of the nonwoven fabric of the present invention may have substantially identical fineness in the range of 4 to 10 denier.

If a nonwoven fabric comprising a first polyester filament of a thick fineness having a relatively high melting point and a second polyester filament of a middle fineness (e.g., 3 to 5 denier) having a relatively low melting point and functioning as an adhesive is made through a spinning-and-mixing method, the nonwoven fabric made as such has relatively small pores. On the other hand, the nonwoven fabric of the present invention comprising the one-component filament and sheath-core type filament both of which have substantially identical fineness has relatively large pores, which reduces the possibility that the filaments of the nonwoven fabric might be damaged during the tufting process.

In sum, if the nonwoven fabric of the present invention is used to make a carpet, the deterioration of the physical properties of the nonwoven fabric, if any, can be remarkably reduced. Thus, the nonwoven fabric of the present invention can be used as an useful primary backing substrate for a carpet since it exhibits good physical properties even after tufting process.

As explained above, the polyester nonwoven fabric of the present invention comprises the sheath-core type filament in addition to the one-component filament. The sheath-core type filament comprises two kinds of polyester polymers. The melting point of the first polyester polymer forming the core component of the sheath-core type filament may be 250° C. or more, preferably 250 to 280° C., and the melting point of the second polyester polymer forming the sheath component of the sheath-core type filament may be lower than that of the first polyester polymer by 20° C. or more. Preferably, the melting point of the second polyester polymer is 180 to 230° C.

If the melting point of the second polyester polymer is too low, heat contraction may occur while the primary backing substrate made from such nonwoven fabric is post-processed, and thus the dimensional stability of the primary backing substrate may be deteriorated. On the contrary, if the melting point of the second polyester polymer is too high, the heating temperature required to melt the sheath component of the sheath-core type filament to bond it to the adjacent filaments increases. If the heating temperature is too high, the physical properties such as tear strength of the nonwoven fabric, especially after the tufting process, is deteriorated.

A conventional polyester polymer having intrinsic viscosity (I.V.) of about 0.655 can be used as the first polyester polymer without any specific limitations. As an illustration, polyethylene terephthalate or polynaphthalene terephthalate may be used as the first polyester polymer. Various polyester polymers other than those also can be used as the first polyester polymer.

For the second polyester polymer, a copolymer having lower melting point than monomers thereof, e.g., a copolymer of one of the aforementioned polyethylene terephthalate and polynaphthalene terephthalate and one of adipic acid and isophthalic acid, or a polymer originally having low melting point such as polybutylene terephthalate and polytrimethylene terephthalate can be used.

According to one embodiment of the present invention, the ratio of the number of the one-component filament to the number of the sheath-core type filament in the polyester nonwoven fabric is 9:1 to 1:9.

If the sheath-core type filaments are more than 9 times as many as the one-component filaments, the nonwoven fabric comprising them would have substantially same physical properties as those of the conventional nonwoven fabric which is formed of only sheath-core type filaments, and thus little improvement can be expected. On the contrary, if the one-component filaments are more than 9 times as many as the sheath-core type filaments, the heating temperature of the heating process to bond the filaments to each other needs to be increased so much that the physical properties of the nonwoven fabric such as tear strength, especially after the tufting process, is deteriorated.

According to the one embodiment of the present invention, the content of the first polyester polymer in the sheath-core type filament is 70 to 95 wt %, and the content of the second polyester polymer therein is 5 to 30 wt %.

Should the content of the second polyester polymer which forms the sheath component of the sheath-core type filament be less than 5 wt %, the bonding power between the filaments would be so weak that it is difficult to make a nonwoven fabric of good physical properties for a primary backing substrate, and there would exist lots of processing limitations since the spinnability during the conjugate spinning process to form the sheath-core type filament would be bad. Further, there would be a problem of weak heat-bonding between the filaments since the content of the core component would be too high to be uniformly surrounded by the sheath component.

On the contrary, should the content of the second polyester polymer be more than 30 wt %, the bonding power between the filaments would be so strong that lots of the filaments are damaged during the tufting process and the physical properties of the nonwoven fabric after the tufting process is seriously deteriorated. Particularly, the content of the first polyester polymer which is the core component of the sheath-core type filament would be so low that the strength of the nonwoven fabric is deteriorated.

Therefore, it is important to maintain the appropriate contents of the core and sheath components in the sheath-core type filament to maintain the physical properties of the filament and whole nonwoven fabric as well as to form an uniform cross section.

The polyester nonwoven fabric comprises the aforementioned filaments the fineness of which is adjusted into 4 to 10 denier and has substantially no filament the fineness of which is out of such range. According to the experiment carried out by us, if the fineness of the filament is less than 4 denier, the number of the filaments per unit area increases and the filaments intersects at so many points that lots of filaments might be damaged by the reciprocating needle during the tufting process thereby resulting in the deterioration of the physical properties of the nonwoven fabric. On the contrary, the filaments of fineness of more than 10 denier makes it difficult to commercially manufacture an uniform nonwoven fabric.

The polyester nonwoven fabric may further comprise an oil coated on the surface of the nonwoven fabric at an amount of 0.2 to 2.0% by weight of the nonwoven fabric. For the oil, a conventional oil comprising an ester compound or a silicon compound as a main component, e.g., polydimethylsiloxane, can be used.

The oil is an element to inhibit the friction between the filaments of the nonwoven fabric and the needle used for the tufting process thereby minimizing the damages of the filaments. If the content of the oil is less than 0.2 wt %, there occurs much friction between the filaments and the needle during the tufting process causing the damages of the filaments. On the contrary, if the content of the oil is more than 2.0 wt %, it would make the nonwoven fabric sticky, and the movement of the oil might be occur when the nonwoven fabric is stored long time.

The polyester nonwoven fabric as explained above may have the same weight per unit area as that of the convention primary backing substrate, i.e., 120 g/m², to have an appropriate physical property such as strength to be used as a primary backing substrate for a carpet.

The polyester nonwoven fabric as described above can be preferably used as a primary backing substrate for a carpet since its filaments are prevented from being damaged during a tufting process to carry a face yarn back and forth through it and thus it can exhibit good physical property even after the tufting process. Furthermore, the polyester nonwoven fabric can be easily made through simple processes at lower costs since its filaments are bonded to each other simply by heating it.

Hereinafter, a method of the present invention for manufacturing a polyester nonwoven fabric will be explained in detail.

A method of the present invention for manufacturing a polyester nonwoven fabric comprises spinning a first polyester polymer to form an one-component filament, conjugate spinning the first polyester polymer and a second polyester polymer to form a sheath-core type filament, the first polyester polymer being a core component and the second polyester polymer being a sheath component, forming a web with the one-component filament and the sheath-core type filament, and heating the web so that the one-component filament and the sheath-core type filament can be bonded to each other.

Through such method, a polyester nonwoven fabric can be made which exhibits good physical properties even after a tufting process. Particularly, the filaments of the nonwoven fabric can easily be bonded to each other simply by applying heat thereto, which makes it needless to perform any other additional process such as a needle punching process for web bonding.

Hereinafter, the method for manufacturing the polyester nonwoven fabric will be explained in more detail.

First, the first and second polyester polymers are melted in their extruders respectively. Then, the first polyester polymer is spun to form an one-component filament, and the first and second polyester polymers are conjugate spun to form a sheath-core type filament. The first polyester polymer forms the core component of the sheath-core type filament, and the second polyester polymer forms the sheath component of the sheath-core type filament. Optionally, the spinning and conjugate spinning may be carried out with one spinneret simultaneously. The spinning and conjugate spinning may be performed at a spinning velocity of 4,500 to 5,000 m/min.

Then, the one-component filament and sheath-core type filament are elongated with a high-pressure air elongator such that the one-component filament and sheath-core type filament can have a fineness of 4 to 10 denier.

Subsequently, a polyester nonwoven fabric is prepared by forming a web with the one-component filament and sheath-core type filament through an opening process and heating the web to bond the filaments to each other.

Although a calendar roll or an emboss roll of high temperature and high pressure may be used as the heat source for bonding the filaments to each other, it is more desirable to use hot air.

If the filaments are heat-bonded by means of a calendar roll or an emboss roll of high temperature and high pressure, the density of the filaments becomes too high due to the tenuity of the nonwoven fabric although the physical properties of the nonwoven fabric such as strength and elongation improves. The high density of the filaments inhibits the movement of the filaments and thus makes the filaments damaged by the needle during the tufting process. Particularly, since the filaments are melted much especially at the part embossed by the roll, the filaments might be seriously damaged when the needle passes therethrough. For this reason, the polyester nonwoven fabric finally obtained as such the physical properties of which would be seriously deteriorated after the tufting process cannot be used as a primary backing substrate for a carpet.

On the other hand, if the filaments are heat-bonded by means of hot air, the second polyester polymer of relatively low melting point at the surface of the sheath-core type filament of the nonwoven fabric is melted and the filaments can be easily bonded without causing any problems mentioned above. Therefore, the polyester nonwoven fabric finally obtained as such can have good initial physical properties and exhibit the good physical properties even after the tufting process.

For the heat-bonding process with hot air, a heat-setting apparatus, e.g., a tenter, blowing out hot air can be used. The temperature of the hot air may be controlled into the degree corresponding to the melting point of the second polyester polymer. Optionally, before the heat-bonding process with hot air is performed, the filaments forming the web may be slightly pressed by means of a calendar roll of low temperature and low pressure to obtain a nonwoven fabric of uniform thickness.

The method for manufacturing a polyester nonwoven fabric may further comprise coating an oil on the surface of the web at an amount of 0.2 to 2.0% by weight of the coated web after the web is heated for bonding the filaments to each other.

As the predetermined amount of the oil is coated on the surface of the nonwoven fabric, the friction between the filaments of the nonwoven fabric and the needle used for the tufting process and the damages of the filaments, if any, that might occur during a tufting process may be further reduced. As a result, the physical properties of the nonwoven fabric after the tufting process can be maintained better.

The polyester nonwoven fabric manufactured according to the present invention can be made good use of as a primary backing substrate for a carpet since it has good initial physical properties and can still exhibit the good physical properties after a tufting process.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The Examples described below are only for the better understanding of the present invention and the present invention should not be restricted to them.

EXAMPLES Example 1

(Preparation of Filaments)

A copolymer of adipic acid and polyethylene terephthalate [Co-PET(AA)/Melting Point: 210° C.] and a polyethylene terephthalate polymer (PET/Melting Point: 255° C.) were melted at 288° C. in the continuous extruders respectively. Then, the PET was spun to form a one-component filament. At the same time, the PET and Co-PET(AA) were conjugate spun to form a sheath-core type filament. The number of the holes of the spinneret and the injection amount therefrom were determined in such a way that the ratio of the number of the one-component filament to the number of the sheath-core type filament was 9:1 and the sheath-core type filament had 85 wt % of PET as a core component and 15 wt % of Co-PET(AA) as a sheath component. Then, the continuous filaments injected from the spinneret were solidified with the cooling air of 25° C. and sufficiently elongated with high pressure air to have fineness of 10 denier at the spinning velocity of 5,000 m/min.

(Preparation of Spunbond Nonwoven Fabric)

A conventional opening method was used to stack the filaments on a continuously moving metal net to form a web. Then, the web was heated by means of a hot air apparatus such that the filaments of the web were bonded to each other at the melting point of the Co-PET(AA). As a result, a polyester nonwoven fabric having a weight per unit area of 120 g/m² was obtained.

(Oiling Process)

The nonwoven fabric prepared as above was treated with an oil. The content of the oil in the nonwoven fabric treated as such was 1.0 wt %.

Example 2

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the contents of the PET and Co-PET(AA) in the sheath-core type filament were 95 wt % and 5 wt % respectively.

Example 3

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the contents of the PET and Co-PET(AA) in the sheath-core type filament were 70 wt % and 30 wt % respectively.

Example 4

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the sheath-core type filament had a copolymer of isophthalic acid and polyethylene terephthalate [Co-PET(IPA)/Melting Point: 208° C.] instead of the Co-PET(AA) as the sheath component and the contents of the PET and Co-PET(IPA) in the sheath-core type filament were 85 wt % and 15 wt % respectively.

Example 5

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the sheath-core type filament had a polybutylene terephthalate polymer (PBT/Melting Point: 224° C.) instead of the Co-PET(AA) as the sheath component and the contents of the PET and PBT in the sheath-core type filament were 85 wt % and 15 wt % respectively.

Example 6

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the sheath-core type filament had a polytrimethylene terephthalate polymer (PTT/Melting Point: 221° C.) instead of the Co-PET(AA) as the sheath component and the contents of the PET and PTT in the sheath-core type filament were 85 wt % and 15 wt % respectively.

Example 7

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the one-component filament and sheath-core type filament had fineness of 4 denier.

Example 8

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the content of the oil in the nonwoven fabric was 0.2 wt %.

Example 9

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the ratio of the number of the one-component filament to the number of the sheath-core type filament was 1:9.

COMPARATIVE EXAMPLES Comparative Example 1

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the one-component filament and sheath-core type filament had fineness of 3 denier.

Comparative Example 2

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the contents of the PET and Co-PET(AA) in the sheath-core type filament were 96 wt % and 4 wt % respectively.

Comparative Example 3

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the contents of the PET and Co-PET(AA) in the sheath-core type filament were 69 wt % and 31 wt % respectively.

Comparative Example 4

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the ratio of the number of the one-component filament to the number of the sheath-core type filament was 91:9.

Comparative Example 5

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the ratio of the number of the one-component filament to the number of the sheath-core type filament was 9:91.

Comparative Example 6

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that the nonwoven fabric was made without the one-component filament and included only the sheath-core type filament.

Comparative Example 7

A polyester nonwoven fabric was made in the same manner as that of the Example 1 except that a PET filament of 10 denier and a Co-PET(AA) filament of 4 denier were respectively formed through a spinning-and-mixing method and the ratio of the weight of the PET filaments to that of the Co-PET(AA) filaments was 85:15.

The physical features of the polyester nonwoven fabrics manufactured in the Examples 1 to 9 and the Comparative Examples 1 to 7 are summarized in Table 1 below.

TABLE 1 Sheath-Core Type Filament Weight One-Component Filament Material of per No. Ratio Sheath No. ratio Unit of Component/ of Conjugate Content Area Material/Melting Filaments Fineness Melting Filaments Fineness Ratio of Oil (g/m²) Point(° C.) (%) (denier) Point(° C.) (%) (denier) (core/sheath) (wt %) Ex. 1 120 PET/255 90 10 Co-PET(AA)/ 10 10 85/15 1.0 210 Ex. 2 120 PET/255 90 10 Co-PET(AA)/ 10 10 95/5  1.0 210 Ex. 3 120 PET/255 90 10 Co-PET(AA)/ 10 10 70/30 1.0 210 Ex. 4 120 PET/255 90 10 Co-PET(IPA)/ 10 10 85/15 1.0 208 Ex. 5 120 PET/255 90 10 PBT/224 10 10 85/15 1.0 Ex. 6 120 PET/255 90 10 PTT/221 10 10 85/15 1.0 Ex. 7 120 PET/255 90 4 Co-PET(AA)/ 10 4 85/15 1.0 210 Ex. 8 120 PET/255 90 10 Co-PET(AA)/ 10 10 85/15 0.2 210 Ex. 9 120 PET/255 10 10 Co-PET(AA)/ 90 10 85/15 1.0 210 Comp. 120 PET/255 90 3 Co-PET(AA)/ 10 3 85/15 1.0 Ex. 1 210 Comp 120 PET/255 90 10 Co-PET(AA)/ 10 10 96/4  1.0 Ex. 2 210 Comp 120 PET/255 90 10 Co-PET(AA)/ 10 10 69/31 1.0 Ex. 3 210 Comp 120 PET/255 91 10 Co-PET(AA)/ 9 10 85/15 1.0 Ex. 4 210 Comp 120 PET/255 9 10 Co-PET(AA)/ 91 10 85/15 1.0 Ex. 5 210 Comp. 120 — Co-PET(AA)/ 100 10 85/15 1.0 Ex. 6 210 Comp. 120 PET/255 85 wt % 10 — 1.0 Ex. 7 Co-PET(AA)/ 15 wt % 4 210 *Note: In the Table 1 above, PET represents polyethylene terephthalate, AA represents adipic acid, IPA represents isophthalic acid, PBT represents polybuthylene terephthalate, and PTT represents polytrimethylene terephthalate.

[Experiments]

The tensile strength, elongation, and tear strength of the polyester nonwoven fabrics manufactured in the Examples 1 to 9 and the Comparative Examples 1 to 7 were respectively measured before and after a tufting process in accordance with the following method, and the results of the measurements are shown Table 2 below.

Experiment 1: Tensile Strength (kgf/5 cm)/Elongation (%)

KS K 0521 method was used to measure the tensile strength and elongation of the polyester nonwoven fabrics. In detail, the tensile strength and elongation of a nonwoven fabric sample having a rectangular shape of 5 cm×20 cm was measured by means of an INSTRON device at the tension speed of 200 mm/min while the sample was held by a 5 cm×5 cm jig.

Experiment 2: Tear Strength (kgf)

KS K 0536 method (Single Tongue method) was used to measure the tear strength of the polyester nonwoven fabrics. In detail, the tear strength of a nonwoven fabric sample having a rectangular shape of 5 cm×20 cm was measured by means of an INSTRON device at the tension speed of 300 mm/min after the sample was cut by 7 cm at the center part thereof.

Experiment 3: Tufting Process

A tufting process was performed on each of the nonwoven fabrics by means of a tufting machine which was set up with 1/10 gauge. After the tufting process, the nonwoven fabrics were tested in accordance with the test methods described in Experiments 1 & 2 above.

TABLE 2 Before Tufting Process After Tufting Process Tensile Tear Tensile Tear Strength Elongation Strength Strength Elongation Strength (kgf/5 cm) (%) (kgf) (kgf/5 cm) (%) (kgf) Comment Ex. 1 26.5/26.9 28.5/29.5 11.5/12.1 18.8/18.7 27.8/28.2 9.1/9.5 ⊚ Ex. 2 26.0/26.1 27.8/28.2 10.5/10.6 18.0/17.3 27.7/29.5 9.0/9.8 ⊚ Ex. 3 27.2/26.5 30.2/32.2 10.7/11.0 17.5/17.6 28.7/27.3 9.0/9.2 ⊚ Ex. 4 27.7/28.2 31.2/33.2 12.1/12.2 18.1/17.3 29.3/31.1 9.2/9.1 ⊚ Ex. 5 25.5/24.5 32.5/35.1 9.1/9.7 16.8/16.6 27.3/29.8 7.1/7.0 ⊚ Ex. 6 27.8/25.1 32.2/33.2 9.2/9.3 16.2/16.1 27.0/29.2 7.0/7.2 ⊚ Ex. 7 26.4/25.1 34.2/36.5 8.5/8.6 14.2/13.7 27.5/26.1 7.0/6.9 ◯ Ex. 8 27.7/28.2 33.5/36.4 9.8/9.7 14.6/14.7 27.9/27.3 6.5/7.0 ◯ Ex. 9 28.5/28.7 32.3/34.1  9.9/10.2 16.5/16.9 27.2/26.9 8.2/7.5 ◯ Comp. 26.1/26.2 35.2/36.6 8.5/8.1 11.2/13.1 22.5/23.1 5.4/5.5 Δ Ex. 1 Comp. 22.1/22.3 25.8/26.2 8.5/7.8 10.0/9.8  20.3/22.3 5.1/4.2 X Ex. 2 Comp. 29.2/30.1 32.2/35.2 10.2/10.7 11.5/11.4 26.7/24.3 5.4/5.1 Δ Ex. 3 Comp. 25.5/25.9 28.1/28.5 10.5/10.1 12.8/12.7 26.8/24.2 6.2/6.9 Δ Ex. 4 Comp. 27.7/28.3 32.2/34.4 9.9/9.9 13.5/13.8 24.4/23.3 5.8/6.3 Δ Ex. 5 Comp. 28.7/29.2 33.5/36.4 9.8/9.7 13.3/12.1 23.2/25.5 5.7/6.1 Δ Ex. 6 Comp. 25.6/24.8 26.7/28.9  9.8/10.5 13.8/13.0 24.8/25.6 6.0/5.8 Δ Ex. 7 *Note: In the Table 2 above, the comment indicates the evaluation of the nonwoven fabric as a primary backing substrate for a carpet. ⊚ means ‘highly suitable,’ ◯ means ‘suitable,’ Δ means ‘unsuitable,’ and X means ‘highly unsuitable.’

Referring to the Table 2 above, it is found that the nonwoven fabrics of the Examples 1 to 9 have good tensile strength, elongation, and tear strength, and such good physical properties are maintained without any meaningful deterioration even after the tufting process.

On the contrary, in cases of the nonwoven fabrics of the Comparative Examples 1 to 3 in which the fineness of the filaments is too small or the content of the second polyester polymer in the sheath-core type filament is too high or too low, it is found that the physical properties of such nonwoven fabrics are bad both before and after the tufting process (Comparative Examples 1 and 2) or that the physical properties of the nonwoven fabric are remarkably deteriorated after the tufting process although it exhibits somewhat good properties before the tufting process (Comparative Example 3). In case of the nonwoven fabric (Comparative Example 4) in which the ratio of the number of the one-component filaments formed of only the first polyester polymer to the number of the sheath-core type filaments formed of the first and second polyester polymers is too low, it is found that its physical properties are relatively low both before and after the tufting process, as is the case in the Comparative Example 7 in which a spinning-and-mixing method was used. In case of the nonwoven fabric (Comparative Example 5) in which the ratio of the number of the one-component filaments formed of only the first polyester polymer to the number of the sheath-core type filaments formed of the first and second polyester polymers is too high, it is found that its physical properties are remarkably deteriorated after the tufting process although it exhibits relatively good properties before the tufting process, as is the case in the Comparative Example 6 in which the nonwoven fabric was formed of only the sheath-core type filaments. It is shown that the nonwoven fabrics of the Comparative Examples are considerably inferior to those made in accordance to the present invention in terms of the tensile strength and tear strength.

Therefore, it is verified that the nonwoven fabrics of the Comparative Examples 1 to 7 cannot be properly used as a primary backing substrate for a carpet since their physical properties including tear strength become significantly low after a tufting process. 

1. A polyester nonwoven fabric comprising: an one-component filament having a fineness of 4 to 10 denier; and a sheath-core type filament having a fineness of 4 to 10 denier, wherein the one-component filament comprises a first polyester polymer having a melting point of 250° C. or higher, wherein the sheath-core type filament comprises the first polyester polymer of 70 to 95 wt % as a core component and a second polyester polymer of 5 to 30 wt % as a sheath component, and wherein a melting point of the second polyester polymer is lower than the melting point of the first polyester polymer by 20° C. or more.
 2. The polyester nonwoven fabric of claim 1, wherein a ratio of a number of the one-component filament to a number of the sheath-core type filament in the polyester nonwoven fabric is 9:1 to 1:9.
 3. The polyester nonwoven fabric of claim 1, wherein the melting point of the first polyester polymer is 250 to 280° C. and the melting point of the second polyester polymer is 180 to 230° C.
 4. The polyester nonwoven fabric of claim 1, wherein the first polyester polymer is polyethylene terephthalate or polynaphthalene terephthalate.
 5. The polyester nonwoven fabric of claim 4, wherein the second polyester polymer is polybutylene terephthalate, polytrimethylene terephthalate, or a copolymer of one of polyethylene terephthalate and polynaphthalene terephthalate and one of adipic acid and isophthalic acid.
 6. The polyester nonwoven fabric of claim 1, further comprising an oil.
 7. The polyester nonwoven fabric of claim 6, wherein the oil comprises a silicon compound.
 8. A method for manufacturing a polyester nonwoven fabric, the method comprising: spinning a first polyester polymer to form an one-component filament; conjugate spinning the first polyester polymer and a second polyester polymer to form a sheath-core type filament, the first polyester polymer being a core component and the second polyester polymer being a sheath component; forming a web with the one-component filament and the sheath-core type filament; and heating the web so that the one-component filament and the sheath-core type filament can be bonded to each other.
 9. The method of claim 8, wherein the spinning and the conjugate spinning are performed simultaneously.
 10. The method of claim 8, further comprising elongating the one-component filament and the sheath-core type filament before forming the web so that the one-component filament and the sheath-core type filament can have a fineness of 4 to 10 denier.
 11. The method of claim 8, wherein the web is heated with hot air.
 12. The method of claim 8, further comprising coating an oil on the heated web. 